Control apparatus



CONTROL APPARATUS Filed April 2l, 193

INVENTORS 0/152 M. M/Y/er.

' A-r'roRyEYs Patented Apr. 3, 1934 UNITED STATES 1,953,425 CONTROLAPPARATUS Ernest M. Miller, Minneapolis, Minn., assignor toMinneapolis-Honeywell Regulator 1 Minneapolis, Minn., a corporation ofCompany, Delaware Application-April 21, 1930, Serial No. 446,160

6 Claims. (Cl. 158-28) This invention relates to burner apparatuscontrolling means. An important object is to provide'means adapted torespond to production of flame at the burner, and when in one positionto permit initiation of burner apparatus operation, including ignition,and when in another position to maintain burner motor operation butdiscontinue ignition, and further adapted to move from the burneroperation maintaining position to another position in a predeterminedperiod of time, and at the end of this time to condition the apparatusfor re-ignition.

Another object is to provide means which, when flame is absent, permitsthe burner apparatus to be started, and when flame is present maintainsburner operation, and which is capable of. timing the interval, betweena shut-down of the apparatus normal or otherwise, and a reenergizationof the same.

Features and advantages of the invention will be set forth in thedescription of the drawing forming a part of this application, and insaid drawing:

Figure 1 is a diagram of the system in its initial position beforeenergization, or before a call for heat by the room thermostat, and

Figure 2 is a perspective view of the combustion responsive switch.

Some of the principal parts of the apparatus will be now referred to,but for sake of brevity the electrical connections will be referred toonly in the description of the operation.

Letters R, B, W, represent the elements of a double contact thermostatadapted to start the apparatus when sufl'i'ciently cold and to stop theapparatus, under normal conditions, when sufficiently hot. Numeral 16indicates any suitable form of ignition. It will be understood thatsuitable fuel supply and control means is provided, although not shown.The term burner apparatus, as used herein, includes the combustionchamber, not shown, the burner motor 17, the ignition l6, and the fuelsupply and control means. The present invention is applicable to anyform of apparatus including the elements referred to.

The numeral 3 indicates the coil of a relay, referred to as relay No. 1,and the numeral 4 indicates the coil of a similar relay, referred to asrelay No. 2. Energization of relay No. 1 establishes a starting circuitfor it, and energizes ignition means and burner motor. Elements 5 and 6represent respectively the switch and the heating coil of a thermalsafety device herein referred to as a thermal safety switch, thefunction of which is to render the whole apparatus inoperative (so thatit cannot be restarted automatically until after inspection and repair)if ignition is not produced at the end of a predetermined period.

An important element of this system is the device generally indicated at7 which is referred to herein as a pyrostat. This device includes thespaced contacts C and H, and the element 8- movable between them. Themovement of the element 8 between the contacts C and H is timed. in thedevice as used, this timing period can be varied. The motion of theelement 8 from its the rod and the opposite end is secured to a tubularextension 8' carried by plate 8. This device is affected by theproduction of flame at the burner. On production of flame the element 8leaves the contact .0 and moves toward the contact H. The device, ofcourse, is properly placed to be affected by the production of flame andin practice is gen-' erally arranged in the stack. It is necessary. forthe element 8 to-close the contact 0 before the apparatus can be startedand this is one of the important features of the invention. Anotherimportant feature is that an appreciable amount of time is required forelement 8 to move from element H to element C upon flame extinguishment,so that before the apparatus can be restarted by closing the contact Cthrough element 8, the accumulated gases in the combustion chamber mayhave time to dissipate. The switch arm 8 may be thermally controlled byany suitable device, providing it is so constructed as to properly timethe motion of the arm from H to C and from C to H. Any suitablecombustion responsive double contact switch may be used, and'there is nointention to be limited to any specific structure for this element. Itis merely noted that the structure and arrangement and proportioning ofthe parts is such that upon cessation of combustion contact of 8 with Cis delayed for the proper time interval.

Operation The operation of the device is as follows; Suppose a call forheat and closure by R of contacts B-W. Relay No. 1 is energized throughthe following circuit: one side of the secondary 2 of thefollows: 2, 20,5, 21, W, R, 30, 10, 31, 14, 25, heating coil 6, 26, 3, 27, 28 to 2. Itis now no longer following circuit: hot line 35, 3'1, contact 11, 38,

contact 12, 42, ignition means 16, 43 to the ground line. Ignition isnow active and a trial ignition period begins, and if not successful atthe end of a predetermined period switch 5 will open as the result ofcontinued heating of coil 6, and-the apparatus will be renderedinoperative, as a result of de-energization of coil 3 of relay No. 1. Inpractice, if this happe the apparatus cannot be restarted until afterinspection, repair and manual operation of a switch, not herein shownbut associated with the thermal safety switch and in, a manner wellknown in this art.

If flame is produced before the end of that predetermined period forwhich switch 5 is set to open, element 8 will move in the direction ofthe arrow and make contact at H, and upon making of this contact, relayNo. 2: will be energized through the following circuit: 2, 20, 5, 21, W,R, 30, 10, 31, 23, 8, H, 45, coil 4. of relay No. 2, 46, 28 to 2.However, on energization of relay No. 2, the circuit of coil 3 is brokenat contact 14 and relay No. 1 falls out opening contact 12 andinterrupting ignition. At the same time, contact 15 is closed and motoroperation is continued through the following circuit: 35, 3'7, 50, 15,51, M

40, motor 1'7, 41 to 36.

Normally the burner apparatus now operates until R opens at W in whichcase relay No.2 opens and the apparatus assumes the initial positionshown in the figure, with the exception that 8 is making contact at H.Under these conditions, the apparatus cannot be again started until 8has moved to contact C which is in the starting circuit and whichcontrols the starting circuit. This is a feature, as is also theprovision of a definite timed period, before contact is again made at C.The apparatus which controls the element 8 canfbe timed and its timeperiod can be adjusted. Therefore, it will take the element 8 apredetermined amount of time to move from H to C. This period is suchthat any explosive gases in the combustion chamber will have beendissipated before ignition means is again made active. This delayedreturn to starting position safeguards against the possibility ofexplosion due to accumulation of vapor, if the flame is extinguishedprematurely or if the burner is started and stopped in quick succession,due to tampering with the thermostat. A safety interval of approximatelyninety seconds is provided and this is controlled by the flameresponsive device; a feature of the invention. An advantage is that themotor is shut down immediately on flame failure due tothe opening ofrelay No. 2. Thus the device herein referred to as a pyrosta is also atimer, and must break its contact each time the burner is shut down. Ifthe contact H should stick or become short-circuited accidentally orintentionally the burner cannot be started because in that case, eithercontact C or contact 14, or both would not be closed. This delayedreturn to starting position by the element 8 is a very important featurebecause the burner cannot be started and stopped in quick succession andthereby develop a hazardous condition. Of course, it will be understoodthat in order to get a start when contact C is closed, the thermostatmust be making contact at WB, and the apparatus must be otherwiseelectrically and mechanically fit.

It will be noted that the starting circuit for relay .No. 1 passesthrough contact C of the pyrostat, contact 14 of relay No. 2 (beforethis relay is, energized) and through heating coil 6 of the thermalsafety switch. Thus, initially, the thermal safety switch is alwaysenergized and relay N0. 2 must be open and contact C of the pyrostatclosed before this can be accomplished. The closing of relay No. 1establishes a holding circuit for itself through contact 10, and sincecontact 14 is at this time closed, this circuit can be maintainedwithout passing through contact C.

Production of flame at the burner closes No. 2 relay, opens the holdingcircuit for No. 1 relay, contact 11 is opened and the ignition means isd'e-energized, motor contact 12 is also opened, but the motor remainsenergized because contact 15 is closed. By the closure of relay No. 2its own holding circuit is established through contact 13 controlled byit, and through contact H of the pyrostat. On closure of No. 2 relay,the heating coil 6 and relay No. 1 are de-energized.

On flame failure, or on a call for less heat by the thermostat, relayNo. 2 falls out due to the breaking of the holding circuit at H; 8 movesfrom H to C and at the end of a predetermined period, the startingcircuit for relay No. 1 is again made. If the thermostat is closed atB-W and if thermal safety switch 5 is closed, relay No. 1 is againenergiz'ed, and if flame is not successful at the end of a predeterminedperiod, thermal safety switch 5 is opened and the plant is shut down inthe usual manner and cannot again be operated automatically until afteradjustment and repair and the manual closing of the thermal safetyswitch.

Although the general combination with the thermal safety switch,including the elements 5 and 6, is also claimed, claim is made tocombinations in which this switch is omitted, for it is evident that byremoving the elements 5 and 6, and connecting lines 20 and 21, and lines25 and 26, the timing function by the flame responsive device 7 can beperformed.

Iclaim as my invention:

1. A device. of the class described comprising 125 a first relay havinga holding contact, a second relay controlling first and second contactsto close the first when the relay is de-energized and to open the firstand close the second when the relay is energized, a switch responsive tovariations in physical conditions and having two contacts operable toclose the first contact on suflicient physical variation in onedirection, and to open the first contact and close the second onsufficient variation in an opposite direction, the variation of thephysical condition in the first direction resulting in opening thesecond contact a timed interval before closing the first contact, anenergizing circuit for the first relay which is dependent on closure ofthe first contacts respectively of said 140 second relay and saidswitch, a. holding circuit for the first relay dependent on closure ofthe holding contact of said first relay and on closure of said firstcontact of the secondrelay, an energizing circuit for the second relaydependent on closure relay and the second contact of said switch.

2. In a burner control system for an igniter and a fuel control means, afirst relay operable to control said igniter and fuel control means andhaving a holding contact, a second relay operable to control said fuelcontrol means only and controlling first and second contacts to closethe first when the relay is de-energized and to open the first and closethe second when the relay is energized, a switch responsive tocombustion conditions, having two contacts and operable to open thefirst contact and close the second on combustion production and to openthe second contact a timed period before closing the first contact oncombustion failure following successful ignition, an energizing circuitfor the first relay which is dependent on closure of the first contactsrespectively of said second relay and said switch, a holdin'g circuitfor the first relay dependent on closure of the holding contact of saidfirst relay and on The closure of said first contact of the secondrelay, an energizing circuit for the second relay dependent on closureof the holding contact of the first relay and on closure of the secondcontact of the switch, and a holding circuit for the second relaydependent on closure of the second contact of said second relay and thesecond contact of said switch, and a safety timer switch adapted torender the system inoperative if flame is not produced at the end of atimed period, including a heater for controlling the timer switch, saidtimer switch being in all control circuits and said heater coil being inthe energizing and holding circuits of said first relay.

3. A first relay having a holding contact, a second relay controllingfirst and second contacts to close the first contact when the relay isdeenergized and to open the first and close the second contact when therelay is energized, a thermally operable switch device having twocontacts operable to open a first and close a second contact ontemperature rise and to close the first contact a timed period afteropening the second contact on temperature fall, a starting circuit forthe first relay-including the first contact of the thermally operabledevice and the first contact of said second relay, a holding circuit forthe first relay including therein the holding contact of said firstrelay and said first contact of said second relay, an energizing circuitfor said second relay including therein the holding contact of the firstrelay and said second contact of said thermally operable device, and aholding circuit for said second relay including therein the secondcontact of said second relay and said second contact of said thermallyoperable device.

4. Ignition means, fuel control means, a first relay operable to controlignition and fuel means and having a holding contact, a second relayoperable to control the fuel means and controlling a double contactswitch to close a first contact when the relay is de-energized and toopen a first and close a second contact when the relay is energized, adevice controlled by combustion conditions having two contacts andoperable to open a first and close a second contact on combustionproduction and on combustion failure to open the second contact a timedperiod before closing the first contact, a starting circuit for thefirst relay including therein said first contact of the combustionresponsive device and the first contact of the second relay, a holdingcircuit for the first relay including therein the holding contact ofsaid first relay and the first contact of said second relay, anenergizing circuit for said second relay including therein the holdingcontact of said first relay, and said second contact of said combustionresponsive device, and a holding circuit for said second relay includingtherein the second contact of said second relay and said second contactof said combustion responsive device.

5. In combination, a burner apparatus including an electric burner motorand an electrically operated igniter, an electrical control systemtherefor including a switch device responsive to flame at the burner andhaving a switch arm and spaced switch contacts, the switch armcontacting a first contact when there is a flame and, on disappearanceof the fiame contacting the second contact after the elapse of a timeperiod; first and second relay switches, said first relay switchoperating when energized to energize said igniter and motor, theoperating circuit of such relay having said second contact and a contactof said second relay switch therein, said relay when energized closing asecond holding circuit including said second relay switch contact butindependent of said second contact; said second relay switch, having anoperating circuit including said first contact, said second relay switchoperating when energized to open said contact in the holding circuit ofsaid first relay switch to deenergize the same and to close a secondcircuit for the burner motor.

6. In a burner control system, a first relay having a holding contactwhich is closed when said relay is energized, a second relay controllingfirst and second contacts to close the first when the relay isde-energized and to open the first and close the second when the relayis energized, switching means responsive to combustion conditions havinga cold switch and a hot switch and operable to open the cold switch andclose the hot switch on establishment of combustion and to open the hotswitch a timed period before closing the cold switch on cessation ofcombustion, a safety timer switch including an electrical heatingelement and adapted to render the system inoperative if said heatingelement is operatively energized for a predetermined length of time, afuel control device, ignition means for igniting the fuel, circuitconnections for initially energizing said first relay and heatingelement controlled by the first contact of the second relay, the safetyswitch, and the cold switch in series, circuit connections formaintaining energization of said first relay and heating elementcontrolled by the holdingcontact of the first relay, the safety switchand the first contact of the second relay in series, an energizingcircuit for the second relay controlled by the holding contact of thefirst relay and said hot switch in series, a holding circuit for saidsecond relay controlled by said 5 second contact of the second relay andsaid hot switch, and connections between v said first relay, secondrelay and fuel control device for operating the latter to initiatesupply fuel upon energization of said first'relay and to maintain thesupply of fuel upon energization of said second relay.

ERNEST M. MILLER.

